The present invention relates to compositions for making fired dental porcelains, to fired dental porcelains themselves, and to processes for making and using fired dental procelains. More particularly, the present invention relates to dental compositions, fired dental procelains and processes providing enhanced bonding of a dental porcelain to a surface of a dental substrate, e.g., the surface of a tooth.
Various techniques and compositions have been used to prepare fired dental porcelains in predetermined shapes for use as, e.g., porcelain veneers, inlays, crowns, dentures and other dental constructions. For example, in an article by Robert Nixon entitled "Use of Porcelain Laminate Veneers Enhances Foreshortened, Worn Teeth," Dentistry Today, October, 1984, pp. 27-31, a general technique of preparing porcelain veneers is discussed. As pointed out in this article, after the porcelain veneers have been formed, baked and glazed, the inner surface of the veneers (i.e., the surface to be attached to the tooth) is etched with a strong acid, usually hydrofluoric acid. While this general technique has provided most times adequate veneer bonding, one drawback of the technique is that the bond between the tooth surface and the etched surface of the porcelain veneer is not always strong. Thus, it would be desirable to be able to provide a stronger bond between the inner veneer surface and the tooth surface (or for that matter the surface of any porcelain to be attached to the surface of a dental substrate).
Another method for making a veneer from a porcelain dental frit material is disclosed in Greggs U.S. Pat. No. 4,473,353. Similar to the general technique discussed in the above paragraph, the Greggs patent in Column 3, lines 62-64 mentions that the inside surface of the veneer can be etched, usually by air abrasion, to promote bonding thereof to the enamel tooth surface.
A laminated veneer is disclosed in Faunce U.S. Pat. No. 4,475,892 in which the veneer is made up of, usually, three laminated layers with each layer including a plurality of elongated vitreous microsized ceramic rods. In connection with FIGS. 7 and 8 of this patent, it is disclosed that the ceramic material may also incorporate combinations of acid soluble glass fibers together with acid resistant glass fibers, with the former being acid etchable. See, for example, Column 5, lines 44-65 of the patent. Such multi-layer veneers, however, have a number of distinct disadvantages, e.g., they are complex in structure and relatively difficult to make. They require relatively highly skilled technicians or even experts to construct them properly. In the dental field, it is highly desirable that veneers and other dental constructions can be made quickly and simple by ordinary technicians so that the cost and time involved for the patient can be minimized. Such laminated veneers as disclosed in the Faunce patent do not provide such desirable characteristics.
Etching has also been used for other purposes in other non-analogous arts, e.g., in the integrated circuit art. See, for example, U.S. Pat. No. 3,650,960. Also, other disclosures have been made in connection with solutions for etching dental porcelain. See, for example, Cheung U.S. Pat. No. 4,376,673.